Digital isolator

ABSTRACT

According to one embodiment, a digital isolator includes a first metal portion, a first insulating portion, a second metal portion, a third metal portion, and a first layer. The first insulating portion is provided on the first metal portion. The second metal portion is provided on the first insulating portion. The third metal portion includes first, second, and third portions. The first portion is provided around the first metal portion in a direction perpendicular to a first direction. The second portion is provided on a portion of the first portion with a first conductive layer interposed. The third portion is provided on the second portion and provided around the second metal portion in the perpendicular direction. The first layer contacts the first conductive layer and an other portion of the first portion and is provided around a bottom portion of the second portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No.2019-169302, filed on Sep. 18, 2019; theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a digital isolator.

BACKGROUND

A digital isolator transmits a signal by utilizing the change of amagnetic field or an electric field in a state in which the current isblocked. It is desirable to increase the reliability of the digitalisolator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view illustrating a digital isolator according to anembodiment;

FIG. 2 is a II-II cross-sectional view of FIG. 1;

FIGS. 3A and 3B are process cross-sectional views illustratingmanufacturing processes of the digital isolator according to theembodiment;

FIGS. 4A and 4B are process cross-sectional views illustratingmanufacturing processes of the digital isolator according to theembodiment;

FIG. 5 is a process cross-sectional view illustrating manufacturingprocesses of the digital isolator according to the embodiment;

FIG. 6 is a cross-sectional view illustrating a digital isolatoraccording to a reference example;

FIG. 7 is a cross-sectional view illustrating a portion of a digitalisolator according to a first modification of the embodiment;

FIGS. 8A and 8B are process cross-sectional views illustratingmanufacturing processes of the digital isolator according to the firstmodification of the embodiment;

FIGS. 9A and 9B are process cross-sectional views illustratingmanufacturing processes of the digital isolator according to the firstmodification of the embodiment;

FIG. 10 is a cross-sectional view illustrating a portion of a digitalisolator according to a second modification of the embodiment:

FIGS. 11A and 11B are process cross-sectional views illustratingmanufacturing processes of the digital isolator according to the secondmodification of the embodiment;

FIGS. 12A and 12B are process cross-sectional views illustratingmanufacturing processes of the digital isolator according to the secondmodification of the embodiment;

FIG. 13 is a cross-sectional view illustrating a portion of a digitalisolator according to a third modification of the embodiment;

FIGS. 14A and 14B are process cross-sectional views illustratingmanufacturing processes of the digital isolator according to the thirdmodification of the embodiment;

FIGS. 15A and 15B are process cross-sectional views illustratingmanufacturing processes of the digital isolator according to the thirdmodification of the embodiment;

FIGS. 16A and 16B are process cross-sectional views illustratingmanufacturing processes of the digital isolator according to the thirdmodification of the embodiment;

FIGS. 17A and 17B are process cross-sectional views illustratingmanufacturing processes of the digital isolator according to the thirdmodification of the embodiment;

FIGS. 18A and 18B are process cross-sectional views illustratingmanufacturing processes of the digital isolator according to the thirdmodification of the embodiment;

FIG. 19 is a cross-sectional view illustrating a portion of a digitalisolator according to a fourth modification of the embodiment;

FIG. 20 is a plan view illustrating a digital isolator according to afifth modification of the embodiment;

FIG. 21 is a plan view illustrating a digital isolator according to afifth modification of the embodiment;

FIG. 22 is a plan view illustrating a digital isolator according to asixth modification of the embodiment;

FIG. 23 is an A1-A2 cross-sectional view of FIG. 22;

FIG. 24 is a B1-B2 cross-sectional view of FIG. 22; and

FIG. 25 is a cross-sectional view illustrating a portion of a digitalisolator according to a seventh modification of the embodiment.

DETAILED DESCRIPTION

According to one embodiment, a digital isolator includes a first metalportion, a first insulating portion, a second metal portion, a thirdmetal portion, and a first layer. The first insulating portion isprovided on the first metal portion. The second metal portion isprovided on the first insulating portion. The third metal portionincludes a first portion, a second portion, and a third portion. Thefirst portion is provided around the first metal portion in a directionperpendicular to a first direction. The first direction is from thefirst metal portion toward the second metal portion. The second portionis provided on a portion of the first portion with a first conductivelayer interposed. The first conductive layer includes tantalum. Thethird portion is provided on the second portion and provided around thesecond metal portion in the perpendicular direction. The first layercontacts the first conductive layer and an other portion of the firstportion and is provided around a bottom portion of the second portion.The first layer includes titanium or includes silicon and carbon.

Various embodiments are described below with reference to theaccompanying drawings.

The drawings are schematic and conceptual; and the relationships betweenthe thickness and width of portions, the proportions of sizes amongportions, etc., are not necessarily the same as the actual values. Thedimensions and proportions may be illustrated differently amongdrawings, even for identical portions.

In the specification and drawings, components similar to those describedpreviously or illustrated in an antecedent drawing are marked with likereference numerals, and a detailed description is omitted asappropriate.

FIG. 1 is a plan view illustrating a digital isolator according to anembodiment.

FIG. 2 is a II-II cross-sectional view of FIG. 1.

As illustrated in FIG. 1 and FIG. 2, the digital isolator 100 accordingto the embodiment includes a first circuit 1, a second circuit 2, afirst metal portion 11, a second metal portion 12, a third metal portion13, a first insulating portion 21, a first layer 31, a second layer 32,a first insulating layer 41, a second insulating layer 42, andconductive layers 51 to 55.

In the digital isolator 100 according to the embodiment, a signal istransmitted in a state in which a current is blocked (insulated) betweenthe first metal portion 11 and the second metal portion 12.

An XYZ orthogonal coordinate system is used in the description of theembodiments. The direction from the first metal portion 11 toward thesecond metal portion 12 is taken as a Z-direction (a first direction).Two mutually-orthogonal directions perpendicular to the Z-direction aretaken as an X-direction (a second direction) and a Y-direction (a thirddirection). For the description, the direction from the first metalportion 11 toward the second metal portion 12 is called “up;” and thereverse direction is called “down.” These directions are based on therelative positional relationship between the first metal portion 11 andthe second metal portion 12 and are independent of the direction ofgravity.

As illustrated in FIG. 2, for example, the first metal portion 11 isprovided inside an insulating portion 20 a. The conductive layer 51 isprovided between the first metal portion 11 and the insulating portion20 a. The first insulating portion 21 is provided on the first metalportion 11 and the insulating portion 20 a. The second metal portion 12is provided on the first insulating portion 21. For example, the secondmetal portion 12 is provided inside an insulating portion 20 b. Theconductive layer 52 is provided between the second metal portion 12 andthe insulating portion 20 b.

In the example illustrated in FIG. 1 and FIG. 2, the first metal portion11 and the second metal portion 12 are coils provided in spiralconfigurations along the X-Y plane. The first metal portion 11 and thesecond metal portion 12 oppose each other in the Z-direction. In otherwords, in FIG. 1 when viewed from the Z-direction, the second metalportion 12 is provided to overlap the first metal portion 11.

As illustrated in FIG. 1, one end of the first metal portion 11 (one endof the coil) is electrically connected to the first circuit 1 via wiring60. An electrode pad 62 is connected to one end of the second metalportion 12 (one end of the coil). For example, the electrode pad 62 isprovided at the inner region of the second metal portion 12. Theelectrode pad 62 may be formed as an integral body with the second metalportion 12. For example, the second circuit 2 and the electrode pad 62are electrically connected via a bonding wire 63.

The third metal portion 13 surrounds the first metal portion 11 and thesecond metal portion 12 in the X-direction and the Y-direction.Specifically, as illustrated in FIG. 2, the third metal portion 13includes a first portion 13 a, a second portion 13 b, and a thirdportion 13 c.

The first portion 13 a is provided around the first metal portion 11 inthe X-direction and the Y-direction. For example, the first portion 13 ais provided inside the insulating portion 20 a. The conductive layer 53is provided between the first portion 13 a and the insulating portion 20a. The other end of the first metal portion 11 (the other end of thecoil) is electrically connected to the first circuit 1 by wiring 61.

The second portion 13 b is provided on a portion of the first portion 13a. The first insulating portion 21 is provided on another portion of thefirst portion 13 a. The conductive layer 54 (a first conductive layer)is provided between the second portion 13 b and the first portion 13 aand between the second portion 13 b and the first insulating portion 21.

The third portion 13 c is provided around the second metal portion 12 inthe X-direction and the Y-direction. For example, the third portion 13 cis provided inside the insulating portion 20 b. The conductive layer 55(a second conductive layer) is provided between the third portion 13 cand the insulating portion 20 b. The other end of the second metalportion 12 is electrically connected to the second circuit 2 by wiring64.

For example, as illustrated in FIG. 1, the first portion 13 a and thethird portion 13 c have ring configurations when viewed from theZ-direction. Multiple second portions 13 b are provided along thering-shaped first portion 13 a and the ring-shaped third portion 13 c.

As illustrated in FIG. 2, the first layer 31 is provided around thebottom portion of the second portion 13 b. The first layer 31 contactsthe conductive layer 54 and the other portion of the first portion 13 arecited above. Therefore, the first insulating portion 21 does notcontact the first portion 13 a and is separated from the first portion13 a in the Z-direction.

The first insulating layer 41 is provided between the first metalportion 11 and the first insulating portion 21. The first insulatinglayer 41 may contact the first metal portion 11 or may be separated fromthe first metal portion 11 in the Z-direction.

The second layer 32 is provided on the first insulating portion 21. Thesecond layer 32 is provided around the bottom portion of the thirdportion 13 c and around the bottom portion of the second metal portion12 and contacts the conductive layers 52 and 55. The second insulatinglayer 42 is provided on the second layer 32 and contacts the conductivelayers 52 and 55.

In the digital isolator 100, the first layer 31 is insulative. The firstlayer 31 is provided also between the first metal portion 11 and thefirst insulating layer 41 and contacts the first metal portion 11. Thefirst insulating layer 41 is positioned between the first layer 31 andthe first insulating portion 21. The first insulating layer 41 isprovided also between the first insulating portion 21 and the otherportion of the first portion 13 a recited above and contacts theconductive layer 54.

One of the first circuit 1 or the second circuit 2 is used as areceiving circuit. The other of the first circuit 1 or the secondcircuit 2 is used as a transmitting circuit. Here, a case will bedescribed where the first circuit 1 is the receiving circuit and thesecond circuit 2 is the transmitting circuit.

The second circuit 2 transmits, to the first metal portion 11, a signal(a current) having a waveform suited to transmission. When the currentflows through the first metal portion 11, a magnetic field that passesthrough the center of the spiral-shaped first metal portion 11 isgenerated. The center position in the X-Y plane of the first metalportion 11 is substantially the same as the center position in the X-Yplane of the second metal portion 12. Therefore, when the magnetic fieldis generated at the first metal portion 11, a portion of the magneticforce lines passes through the inner region of the second metal portion12. An induced electromotive force is generated in the second metalportion 12 by the change of the magnetic field at the inner region ofthe second metal portion 12; and a current flows through the secondmetal portion 12. The first circuit 1 detects the current flowingthrough the second metal portion 12 and generates a signal correspondingto the detection result. Thereby, the signal is transmitted in the statein which the current is blocked (insulated) between the first metalportion 11 and the second metal portion 12.

The third metal portion 13 is connected to a reference potential. Thereference potential is, for example, the ground potential. Because thethird metal portion 13, which is connected to the reference potential,is provided around the first metal portion 11 and the second metalportion 12, leakage of the magnetic field outside the digital isolator100 can be suppressed.

Examples of the materials of the components of the digital isolator 100will now be described.

The first metal portion 11, the second metal portion 12, and the thirdmetal portion 13 include metals. To suppress the heat generation of thefirst metal portion 11 and the second metal portion 12 when transmittingthe signal, it is favorable for the electrical resistances of thesemetal portions to be low. From the perspective of reducing theelectrical resistances, it is favorable for the first metal portion 11and the second metal portion 12 to include copper.

The first insulating portion 21, the insulating portion 20 a, and theinsulating portion 20 b include, for example, an insulating materialincluding oxygen and silicon. The first insulating portion 21, theinsulating portion 20 a, and the insulating portion 20 b include, forexample, an insulating material such as silicon oxide, etc. Theinsulating portion 20 a may be at least a portion of a substrate.

The conductive layers 51 to 55 include tantalum. The conductive layers51 to 55 may include a nitride of tantalum. The conductive layers 51 to55 may have a stacked structure of tantalum and a nitride of tantalum.The conductive layers 51 to 55 suppress the diffusion into the firstinsulating portion 21, the insulating portion 20 a, and the insulatingportion 20 b of the metals included in the first to third metal portions11 to 13.

The first layer 31 and the second layer 32 include carbon, silicon, andat least one selected from the group consisting of oxygen and nitrogen.For example, the first layer 31 and the second layer 32 include SiCO,SiCN, or SiCON. The material that is included in the second layer 32 maybe different from the material included in the first layer 31.

The first insulating layer 41 and the second insulating layer 42 includesilicon nitride.

The carbon concentration in the first layer 31 is higher than the carbonconcentration in the first insulating layer 41. The hardness can bereduced by adding more carbon to the insulating layers. Therefore, theYoung's modulus of the first layer 31 is lower than the Young's modulusof the first insulating layer 41. Similarly, the carbon concentration inthe second layer 32 is higher than the carbon concentration in thesecond insulating layer 42 and higher than the carbon concentration inthe first insulating layer 41. Therefore, the Young's modulus of thesecond layer 32 is lower than the Young's modulus of the secondinsulating layer 42 and lower than the Young's modulus of the firstinsulating layer 41. The carbon concentration in the first layer 31 maybe the same as or different from the carbon concentration in the secondlayer 32. On the other hand, to improve the insulative properties, it isfavorable for the first insulating layer 41 and the second insulatinglayer 42 to be formed without adding carbon.

For example, the carbon concentration in the first layer 31 and thecarbon concentration in the second layer 32 each are not less than 15atom % and not more than 25 atom % in atomic composition percent. Thecarbon concentration in the first insulating layer 41 and the carbonconcentration in the second insulating layer 42 each are not less than 0atom % and not more than 10 atom % in atomic composition percent.

For example, a thickness T1 in the Z-direction of the first layer 31 isgreater than a thickness T2 in the Z-direction of the conductive layer54. The thickness T2 is measured based on a portion of the conductivelayer 54 positioned between the first portion 13 a and the secondportion 13 b in the Z-direction. For example, a thickness T3 of thefirst insulating layer 41 is greater than the thickness T2. Thethickness T1 and the thickness T3 each are smaller than a thickness T4of the first insulating portion 21.

For example, a thickness T5 in the Z-direction of the second layer 32 isthicker than a thickness T6 in the Z-direction of the conductive layer55. The thickness T6 is measured based on a portion of the conductivelayer 55 positioned between the second portion 13 b and the thirdportion 13 c in the Z-direction. For example, a thickness T7 of thesecond insulating layer 42 is thicker than the thickness T6. Thethickness T5 and the thickness T7 each are smaller than the thickness T4of the first insulating portion 21.

An example of a method for manufacturing the digital isolator accordingto the embodiment will now be described.

FIG. 3A to FIG. 5 are process cross-sectional views illustratingmanufacturing processes of the digital isolator according to theembodiment.

First, an insulative substrate S is prepared. For example, a siliconsubstrate can be used as the substrate S. The first circuit 1 is formedin the substrate S. The insulating portion 20 a is formed on thesubstrate S. An opening is formed in the insulating portion 20 a byreactive ion etching (RIE). The opening includes a spiral-shapedportion, and a ring-shaped portion surrounding the spiral-shapedportion. A conductive layer is formed along the inner surface of theopening and the upper surface of the insulating portion 20 a bysputtering. A metal layer that fills the opening is formed on theconductive layer by sputtering and electroplating. The upper surface ofthe metal layer and the upper surface of the conductive layer are causedto recede by chemical mechanical polishing (CMP) until the upper surfaceof the insulating portion 20 a is exposed. As illustrated in FIG. 3A,the first metal portion 11, the conductive layer 51, the first portion13 a, and the conductive layer 53 are formed thereby.

The first layer 31 that covers the first metal portion 11 and the firstportion 13 a is formed on the insulating portion 20 a by chemical vapordeposition (CVD). For example, a gas that includes carbon and siliconsuch as trimethylsilane or the like, a nitrogen-including gas such asammonia (NH₃) or the like, and an inert gas are supplied onto theinsulating portion 20 a. The first layer 31 that includes SiCN is formedthereby. The first insulating layer 41 that includes silicon nitride isformed on the first layer 31 by CVD. As illustrated in FIG. 3B, thefirst insulating portion 21 is formed on the first insulating layer 41by CVD.

An opening is formed above the first portion 13 a by removing a portionof the first insulating portion 21 by RIE. At this time, the firstinsulating layer 41 functions as a stopper. A portion of the exposedfirst insulating layer 41 and a portion of the first layer 31 areremoved via the opening by wet etching or RIE. In the case where wetetching is performed, a mixed liquid of ammonium fluoride (NH₄F),hydrogen fluoride (HF), and water (H₂O), a mixed liquid of hydrogenfluoride (HF) and water (H₂O), or phosphoric acid (H₃PO₄) can be used asthe etchant. In the case where RIE is performed, a gas that includes afluorinated saturated hydrocarbon such as CHF₃, CH₂F₂, C₄H₉F, or thelike is used as the etching gas.

A portion of the upper surface of the first portion 13 a is exposed viathe opening. A conductive layer is formed along the inner surface of theopening and the upper surface of the first insulating portion 21 bysputtering. A metal layer that fills the opening is formed on theconductive layer by sputtering and electroplating. The upper surface ofthe metal layer and the upper surface of the conductive layer are causedto recede by CMP until the upper surface of the first insulating portion21 is exposed. As illustrated in FIG. 4A, the second portion 13 b andthe conductive layer 54 are formed thereby.

Similarly to the first layer 31, the second layer 32 is formed on thesecond portion 13 b and the first insulating portion 21 by CVD. Thesecond insulating layer 42 is formed on the second layer 32 by CVD. Asillustrated in FIG. 4B, the insulating portion 20 b is formed on thesecond insulating layer 42 by CVD.

An opening is formed above the first metal portion 11 and the secondportion 13 b by removing a portion of the insulating portion 20 b byRIE. The opening includes a spiral-shaped portion, and a ring-shapedportion surrounding the spiral-shaped portion. When forming the opening,the second insulating layer 42 functions as a stopper. A portion of theexposed second insulating layer 42 and a portion of the second layer 32are removed via the opening by wet etching or RIE. The chemical liquidor the gas for removing the first layer 31 and the first insulatinglayer 41 described above can be used as the etchant or the etching gas.

A conductive layer is formed along the inner surface of the opening andthe upper surface of the insulating portion 20 b by sputtering. A metallayer that fills the opening is formed on the conductive layer bysputtering and electroplating. The upper surface of the metal layer andthe upper surface of the conductive layer are caused to recede by CMPuntil the upper surface of the insulating portion 20 b is exposed. Asillustrated in FIG. 5, the second metal portion 12, the electrode pad62, the conductive layer 52, the third portion 13 c, and the conductivelayer 55 are formed thereby. By the processes recited above, the digitalisolator 100 illustrated in FIG. 1 and FIG. 2 is manufactured.

A protective film may be formed on the second metal portion 12, theelectrode pad 62, the conductive layer 52, the third portion 13 c, andthe conductive layer 55. In such a case, an opening is provided byremoving the protective film on the electrode pad 62. An insulating filmmay be formed on the second metal portion 12, the conductive layer 52,the third portion 13 c, and the conductive layer 55; and a wiring layerthat includes an electrode pad may be formed on the insulating film.

Effects of the embodiment will now be described with reference to FIG.6.

FIG. 6 is a cross-sectional view illustrating a digital isolatoraccording to a reference example.

The first layer 31 and the second layer 32 are not provided in thedigital isolator 100 r according to the reference example illustrated inFIG. 6. The first insulating layer 41 is provided around the bottomportion of the second portion 13 b. The first insulating layer 41contacts the first portion 13 a and the conductive layer 54. The secondinsulating layer 42 is provided around the bottom portion of the thirdportion 13 c. The second insulating layer 42 contacts the firstinsulating portion 21 and the conductive layer 55.

The first insulating layer 41 includes silicon nitride. By contactingthe first portion 13 a, the first insulating layer 41 can suppress thediffusion from the first portion 13 a of the metal atoms included in thefirst portion 13 a into the first insulating portion 21 and theinsulating portion 20 a. Thereby, the leakage current due to thediffusion of the metal atoms can be reduced; and the reliability of thedigital isolator 100 r can be increased.

On the other hand, the conductive layer 54 which includes tantalum hashigh compressive stress. The conductive layer 54 is provided along theX-Y plane at the bottom portion of the second portion 13 b. Therefore,at the bottom portion of the second portion 13 b, the conductive layer54 applies stress to the other members along the X-Y plane. Also,thermal expansion of the third metal portion 13 occurs when heat isgenerated as the digital isolator 100 is used. Therefore, in the digitalisolator 100 r, a large stress is applied from the first portion 13 a ofthe third metal portion 13 and the conductive layer 54 to the firstinsulating layer 41. The first insulating layer 41 has a dense structureand a high Young's modulus. When the large stress is applied to thefirst insulating layer 41, there is a possibility that the stress maynot be dispersed sufficiently; and the first insulating layer 41 maypeel.

In the digital isolator 100 according to the embodiment, the first layer31 is provided around the bottom portion of the second portion 13 b. Bycontacting the first portion 13 a around the bottom portion of thesecond portion 13 b, the first layer 31 can suppress the diffusion ofthe metal atoms included in the first portion 13 a. Also, the carbonconcentration in the first layer 31 is higher than the carbonconcentration in the first insulating layer 41. Therefore, the Young'smodulus of the first layer 31 is lower than the Young's modulus of thefirst insulating layer 41. Even when stress is applied from the firstportion 13 a and the conductive layer 54, the first layer 31 deformseasily and does not peel easily compared to the first insulating layer41. By providing the first layer 31, the peeling of the first insulatinglayer 41 can be suppressed; and the reliability of the digital isolator100 can be increased.

Similarly, in the digital isolator 100 r according to the referenceexample, the second insulating layer 42 is subjected to stress from theconductive layer 55 around the bottom portion of the third portion 13 c.Thereby, there is a possibility that peeling of the second insulatinglayer 42 may occur. In the digital isolator 100 according to theembodiment, the second layer 32 is provided around the bottom portion ofthe third portion 13 c. The carbon concentration in the second layer 32is higher than the carbon concentration in the second insulating layer42. Therefore, the Young's modulus of the second layer 32 is lower thanthe Young's modulus of the second insulating layer 42. By providing thesecond layer 32, even when the stress is applied from the conductivelayer 55, the peeling of the second insulating layer 42 can besuppressed; and the reliability of the digital isolator 100 can beincreased.

Compared to the first layer 31, the first insulating layer 41 has adense structure in which the added amount of carbon is low. Therefore,the electrical resistance of the first insulating layer 41 is higherthan the electrical resistance of the first layer 31. By providing thefirst insulating layer 41 between the first metal portion 11 and thefirst insulating portion 21, the electrical resistance between the firstmetal portion 11 and the second metal portion 12 can be increased; andthe leakage current between these metal portions can be reduced.

In the digital isolator 100, the first layer 31 is provided also betweenthe first metal portion 11 and the first insulating layer 41; and thefirst insulating layer 41 is provided also between the first portion 13a and the first insulating portion 21. According to this structure,patterning of the first layer 31 and the first insulating layer 41 isunnecessary when forming the first layer 31 and the first insulatinglayer 41. Therefore, the number of processes necessary for manufacturingthe digital isolator 100 can be reduced.

The first insulating layer 41 is provided between the first metalportion 11 and the second metal portion 12 even in the case where thefirst layer 31, which has a lower electrical resistance than the firstinsulating layer 41, is provided between the first metal portion 11 andthe second metal portion 12. Thereby, the electrical resistance betweenthe first metal portion 11 and the second metal portion 12 can beincreased; and the leakage current between these metal portions can bereduced.

A portion of the conductive layer 54 extends in the Z-direction betweenthe second portion 13 b and the first insulating portion 21. The firstinsulating layer 41 contacts the portion of the conductive layer 54.Because the portion of the conductive layer 54 extends in theZ-direction, the stress that acts toward the X-direction and theY-direction is not large. The stress that is applied from the conductivelayer 54 to the first insulating layer 41 is smaller than the stressapplied from the conductive layer 54 to the first layer 31. Therefore,as long as the first layer 31 is provided, the first insulating layer 41may contact the conductive layer 54.

Similarly, a portion of the conductive layer 55 extends in theZ-direction between the third portion 13 c and the insulating portion 20b; and the second insulating layer 42 contacts the portion of theconductive layer 55. However, the stress that is applied from theconductive layer 55 to the second insulating layer 42 is smaller thanthe stress applied from the conductive layer 55 to the second layer 32.Therefore, as long as the second layer 32 is provided, the secondinsulating layer 42 may contact the conductive layer 55.

First Modification

FIG. 7 is a cross-sectional view illustrating a portion of a digitalisolator according to a first modification of the embodiment.

In the digital isolator 110 according to the first modification, thefirst layer 31 is provided only around the bottom portion of the secondportion 13 b. In other words, the first layer 31 is not provided betweenthe first metal portion 11 and the second metal portion 12. A portion ofthe first insulating layer 41 is provided between the first metalportion 11 and the first insulating portion 21; and another portion ofthe first insulating layer 41 is provided between the first layer 31 andthe first insulating portion 21.

Similarly, the second layer 32 is provided only around the bottomportion of the third portion 13 c. The second layer 32 is not providedaround the bottom portion of the second metal portion 12 and isseparated from the second metal portion 12. A portion of the secondinsulating layer 42 is provided around the bottom portion of the secondmetal portion 12; and another portion of the second insulating layer 42is provided on the second layer 32.

FIGS. 8A and 8B are process cross-sectional views illustratingmanufacturing processes of the digital isolator according to the firstmodification of the embodiment.

First, the first metal portion 11, the conductive layer 51, the firstportion 13 a, and the conductive layer 53 are formed by performingprocesses similar to the processes illustrated in FIG. 3A. The firstlayer 31 that covers the first metal portion 11 and the first portion 13a is formed by CVD. As illustrated in FIG. 8A, a portion of the firstlayer 31 is removed by RIE to expose the first metal portion 11. Asillustrated in FIG. 8B, the first insulating layer 41 is formed on thefirst metal portion 11 and the first layer 31 by CVD.

The first insulating portion 21 is formed on the first insulating layer41 by CVD. The second portion 13 b and the conductive layer 54 areformed by performing processes similar to the processes illustrated inFIG. 4A. The second layer 32 that covers the second portion 13 b and thefirst insulating portion 21 is formed by CVD. As illustrated in FIG. 9A,a portion of the second layer 32 positioned above the first metalportion 11 is removed by RIE. As illustrated in FIG. 8B, the secondinsulating layer 42 is formed on the first insulating portion 21 and thesecond layer 32 by CVD. The insulating portion 20 b is formed on thesecond insulating layer 42 by CVD. Thereafter, the digital isolator 110according to the first modification is manufactured by performingprocesses similar to the processes illustrated in FIG. 5.

The carbon concentration in the first layer 31 is higher than the carbonconcentration in the first insulating layer 41. Therefore, theelectrical resistivity of the first layer 31 is lower than theelectrical resistivity of the first insulating layer 41. Because thefirst layer 31 is provided between the first metal portion 11 and thefirst insulating layer 41, there is a possibility that a leakage currentmay flow between the first metal portion 11 and the third metal portion13 via the first layer 31.

Heat is generated if a leakage current flows between the first metalportion 11 and the third metal portion 13. The heat that is generatedincreases as the leakage current increases. Therefore, particularly whena high voltage is applied between the first metal portion 11 and thesecond metal portion 12, the heat generation increases, which may causeoperation errors of the digital isolator, etc.

In the digital isolator 110, the first layer 31 is not provided betweenthe first metal portion 11 and the second metal portion 12. Therefore,the flow of the leakage current between the first metal portion 11 andthe third metal portion 13 via the first layer 31 can be suppressed.Thereby, the heat generation due to the leakage current can be reduced;and the reliability of the digital isolator 110 can be increased.

Similarly to the first layer 31, the electrical resistivity of thesecond layer 32 is lower than the electrical resistivity of the secondinsulating layer 42. The second layer 32 is not provided around thebottom portion of the second metal portion 12 and is separated from thesecond metal portion 12. Therefore, the flow of a leakage currentbetween the second metal portion 12 and the third metal portion 13 viathe second layer 32 can be suppressed. The reliability of the digitalisolator 110 can be increased thereby.

In the digital isolator 110, the first layer 31 is separated from thefirst metal portion 11. Therefore, the first layer 31 may be conductiveor semiconductive. Similarly, the second layer 32 may be conductive orsemiconductive. For example, the first layer 31 and the second layer 32are semiconductive and include silicon and carbon. Or, the first layer31 and the second layer 32 are conductive and include titanium. Thefirst layer 31 and the second layer 32 may include a nitride oftitanium. Also, the material that is included in the second layer 32 maybe different from the material included in the first layer 31.

When the first layer 31 is semiconductive or conductive, the first layer31 is electrically connected to the third metal portion 13; and thepotential of the first layer 31 is fixed to the reference potential. Ifthe distance between the first layer 31 and the first metal portion 11is short, there is a possibility that the electric field intensitybetween the first layer 31 and the first metal portion 11 may increase.Accordingly, when the first layer 31 is conductive or semiconductive, itis favorable for the first layer 31 and the first metal portion 11 to beseparated sufficiently according to the voltage generated by the firstmetal portion 11. Similarly, when the second layer 32 is semiconductiveor conductive, it is favorable for the second layer 32 and the secondmetal portion 12 to be separated sufficiently according to the voltageapplied to the second metal portion 12.

Second Modification

FIG. 10 is a cross-sectional view illustrating a portion of a digitalisolator according to a second modification of the embodiment.

In the digital isolator 120 according to the second modification asillustrated in FIG. 10, the first insulating layer 41 does not contactthe conductive layer 54 and is separated from the conductive layer 54.For example, the first insulating layer 41 does not overlap the firstlayer 31 in the Z-direction and is arranged with the first layer 31 inthe X-direction and the Y-direction. The first insulating layer 41 maycontact the first layer 31 or may be separated from the first layer 31.

Similarly, the second insulating layer 42 does not contact theconductive layer 55 and is separated from the conductive layer 55. Forexample, the second insulating layer 42 does not overlap the secondlayer 32 in the Z-direction and is arranged with the second layer 32 inthe X-direction and the Y-direction. The second insulating layer 42 maycontact the second layer 32 or may be separated from the second layer32.

FIG. 11A to FIG. 12B are process cross-sectional views illustratingmanufacturing processes of the digital isolator according to the secondmodification of the embodiment.

As illustrated in FIG. 11A, the first layer 31 and the first insulatinglayer 41 are formed by performing processes similar to the processesillustrated in FIG. 3A, FIG. 8A, and FIG. 8B. As illustrated in FIG.11B, a portion of the first insulating layer 41 provided on the firstlayer 31 is removed by RIE. At this time, the RIE may be performed sothat the first insulating layer 41 after the removal is separated fromthe first layer 31.

The first insulating portion 21 is formed on the first layer 31 and thefirst insulating layer 41 by CVD. As illustrated in FIG. 12A, the secondportion 13 b, the conductive layer 54, the second layer 32, and thesecond insulating layer 42 are formed by performing processes similar tothe processes illustrated in FIG. 4A, FIG. 9A, and FIG. 9B. Asillustrated in FIG. 12B, a portion of the second insulating layer 42provided on the second layer 32 is removed by RIE. At this time, the RIEmay be performed so that the second insulating layer 42 after theremoval is separated from the second layer 32. The insulating portion 20b is formed on the second layer 32 and the second insulating layer 42 byCVD. Thereafter, the digital isolator 120 according to the secondmodification is manufactured by performing processes similar to theprocesses illustrated in FIG. 5.

Because the first insulating layer 41 is separated from the conductivelayer 54, application of the stress from the conductive layer 54 to thefirst insulating layer 41 can be avoided. The peeling of the firstinsulating layer 41 due to the stress applied from the conductive layer54 can be prevented more reliably thereby. Similarly, because the secondinsulating layer 42 is separated from the conductive layer 55,application of the stress from the conductive layer 55 to the secondinsulating layer 42 can be avoided. The peeling of the second insulatinglayer 42 due to the stress applied from the conductive layer 55 can beprevented more reliably thereby.

Third Modification

FIG. 13 is a cross-sectional view illustrating a portion of a digitalisolator according to a third modification of the embodiment.

In the digital isolator 130 according to the third modification, thefirst insulating layer 41 is provided on the first metal portion 11 andaround the bottom portion of the second portion 13 b and contacts thefirst portion 13 a. The second insulating layer 42 is provided aroundthe bottom portion of the third portion 13 c and around the bottomportion of the second metal portion 12. In other words, the first layer31 and the second layer 32 are not provided in the digital isolator 130.

A gap G1 is provided between the first insulating layer 41 and theconductive layer 54. Therefore, the first insulating layer 41 isseparated from the conductive layer 54 in the X-direction and theY-direction. Similarly, a gap G2 is provided between the secondinsulating layer 42 and the conductive layer 55. Therefore, the secondinsulating layer 42 is separated from the conductive layer 55 in theX-direction and the Y-direction.

FIG. 14A to FIG. 18B are process cross-sectional views illustratingmanufacturing processes of the digital isolator according to the thirdmodification of the embodiment.

First, the first metal portion 11, the conductive layer 51, the firstportion 13 a, and the conductive layer 53 are formed by performingprocesses similar to the processes illustrated in FIG. 3A. Asillustrated in FIG. 14A, the first insulating layer 41 that covers thefirst metal portion 11 and the first portion 13 a is formed by CVD. Thefirst insulating portion 21 is formed on the first insulating layer 41by CVD. As illustrated in FIG. 14B, an opening OP1 is formed by removinga portion of the first insulating portion 21 and a portion of the firstinsulating layer 41 by RIE.

A portion of the first insulating layer 41 is removed via the openingOP1 by isotropic etching such as wet etching, chemical dry etching(CDE), etc. The chemical liquid or the gas for removing the first layer31 and the first insulating layer 41 described above can be used as theetchant or the etching gas. Thereby, as illustrated in FIG. 15A, the endsurface of the first insulating layer 41 exposed in the opening OP1recedes. By the end surface of the first insulating layer 41 receding,the bottom portion side surface of the opening OP1 is recessedpartially.

As illustrated in FIG. 15B, a conductive layer CL1 is formed along theinner surface of the opening OP1 and the upper surface of the firstinsulating portion 21 by sputtering. At this time, the recess of thebottom portion side surface of the opening OP1 is plugged with theconductive layer CL1; and the gap G1 is formed. A metal layer that fillsthe opening OP1 is formed on the conductive layer CL1 by sputtering andelectroplating. The upper surface of the metal layer and the uppersurface of the conductive layer CL1 are caused to recede by CMP untilthe upper surface of the first insulating portion 21 is exposed.Thereby, the second portion 13 b and the conductive layer 54 are formedas illustrated in FIG. 16A.

The second insulating layer 42 and the insulating portion 20 b areformed on the second portion 13 b and the first insulating portion 21 byCVD. As illustrated in FIG. 16B, an opening OP2 is formed above thefirst metal portion 11 and the second portion 13 b by removing a portionof the insulating portion 20 b and a portion of the second insulatinglayer 42 by RIE.

As illustrated in FIG. 17A, a mask M that covers the opening formedabove the first metal portion 11 is formed. The opening that is formedabove the second portion 13 b is not covered with the mask M and isexposed. A portion of the second insulating layer 42 is removed via theopening OP2 by isotropic etching. The chemical liquid or the gas forremoving the first layer 31 and the first insulating layer 41 describedabove can be used as the etchant or the etching gas. Thereby, asillustrated in FIG. 17B, the end surface of the second insulating layer42 exposed in the opening OP2 recedes. Due to the end surface of thesecond insulating layer 42 receding, the bottom portion side surface ofthe opening OP2 is recessed partially.

The mask M is removed; and a conductive layer CL2 is formed along theinner surface of the opening OP2 and the upper surface of the insulatingportion 20 b by sputtering as illustrated in FIG. 18A. At this time, therecess of the bottom portion side surface of the opening OP2 is pluggedwith the conductive layer CL2; and a gap G2 is formed. A metal layerthat fills the opening OP2 is formed on the conductive layer CL2 bysputtering and electroplating. The upper surface of the metal layer andthe upper surface of the conductive layer CL2 are caused to recede byCMP until the upper surface of the insulating portion 20 b is exposed.Thereby, the third portion 13 c and the second metal portion 12 areformed as illustrated in FIG. 18B. Thus, the digital isolator 130according to the third modification is manufactured.

In the digital isolator 130, the first insulating layer 41 is separatedfrom the conductive layer 54. Therefore, the first insulating layer 41is not subjected to stress from the conductive layer 54. Accordingly,the peeling of the first insulating layer 41 caused by the stress of theconductive layer 54 can be suppressed. Similarly, because the secondlayer 32 is separated from the conductive layer 55, the second layer 32is not subjected to stress from the conductive layer 55. Accordingly,the peeling of the second insulating layer 42 caused by the stress ofthe conductive layer 55 can be suppressed.

Fourth Modification

FIG. 19 is a cross-sectional view illustrating a portion of a digitalisolator according to a fourth modification of the embodiment.

In the digital isolator 140 according to the fourth modification, thefirst insulating layer 41 and the second insulating layer 42 are notprovided as illustrated in FIG. 19. The first layer 31 is providedaround the bottom portion of the second portion 13 b and between thefirst metal portion 11 and the first insulating portion 21. The secondlayer 32 is provided around the bottom portion of the third portion 13 cand around the bottom portion of the second metal portion 12. The firstlayer 31 and the second layer 32 are insulative.

By providing the first layer 31, the diffusion of the metal atomsincluded in the first portion 13 a and the first metal portion 11 intothe first insulating portion 21 and the insulating portion 20 a can besuppressed, The second layer 32 functions as a stopper when forming theopening for forming the second metal portion 12 and the third portion 13c. Because the first insulating layer 41 and the second insulating layer42 which have relatively high Young's moduli are not provided, thepeeling of the layers can be suppressed; and the reliability of thedigital isolator 140 can be increased,

However, to reduce the leakage current, it is favorable for the firstinsulating layer 41 to be provided. Even when the first insulating layer41 is provided, the peeling of the first insulating layer 41 can besuppressed sufficiently by providing the first layer 31.

Fifth Modification

FIG. 20 and FIG. 21 are plan views illustrating digital isolatorsaccording to a fifth modification of the embodiment,

In a digital isolator 151 illustrated in FIG. 20, the other end of thefirst metal portion 11 is electrically connected to the first portion 13a of the third metal portion 13 via the wiring 61. The other end of thesecond metal portion 12 is electrically connected to the second circuit2 via the wiring 64. The other end of the first metal portion 11 may beconnected to the reference potential by wiring, etc., other than thethird metal portion 13.

In a digital isolator 152 illustrated in FIG. 21, the other end of thesecond metal portion 12 is electrically connected to the third portion13 c of the third metal portion 13 via the wiring 64. The other end ofthe first metal portion 11 is electrically connected to the firstcircuit 1 via the wiring 61. The other end of the second metal portion12 may be connected to the reference potential by wiring, etc., otherthan the third metal portion 13.

As illustrated in FIG. 20 and FIG. 21, one of the first metal portion 11or the second metal portion 12 may be electrically connected to thethird metal portion 13. In such a case as well, similarly to the digitalisolator 100, the signal can be transmitted in the state in which thecurrent is blocked (insulated) between the first metal portion 11 andthe second metal portion 12.

Sixth Modification

FIG. 22 is a plan view illustrating a digital isolator according to asixth modification of the embodiment.

FIG. 23 is an A1-A2 cross-sectional view of FIG. 22.

FIG. 24 is a B1-B2 cross-sectional view of FIG. 22.

The digital isolator 160 according to the sixth modification includesthe first circuit 1, the second circuit 2, and a pair of structurebodies 10 (10-1 and 10-2).

As illustrated in FIG. 22 and FIG. 23, the structure body 10-1 includesthe first metal portion 11, the second metal portion 12, the third metalportion 13, the first insulating portion 21, the first layer 31, thesecond layer 32, the first insulating layer 41, the second insulatinglayer 42, and conductive layers 51 a to 55 a. The configurations of thecomponents of the structure body 10-1 are similar to those of one of thedigital isolators 100 to 130. For example, as illustrated in FIG. 23,the configuration of the A1-A2 cross section of the structure body 10-1is similar to the configuration of the II-II cross section of thedigital isolator 100 illustrated in FIG. 2. Or, the configuration of thestructure body 10-1 may be similar to the digital isolator 140; and thefirst insulating layer 41 and the second insulating layer 42 may not beprovided in the structure body 10-1.

The structure body 10-2 includes a fourth metal portion 14, a fifthmetal portion 15, a sixth metal portion 16, a second insulating portion22, a third layer 33, a fourth layer 34, a third insulating layer 43, afourth insulating layer 44, and conductive layers 51 b to 55 b. Theconfigurations of the components of the structure body 10-2 are similarto those of one of the digital isolators 100 to 130. For example, asillustrated in FIG. 24, the configuration of the B1-B2 cross section ofthe structure body 10-2 is similar to the configuration of the II-IIcross section of the digital isolator 100 illustrated in FIG. 2.

In other words, as illustrated in FIG. 24, for example, the fourth metalportion 14 is provided inside an insulating portion 20 c. The conductivelayer 51 b is provided between the fourth metal portion 14 and theinsulating portion 20 c. The second insulating portion 22 is provided onthe fourth metal portion 14 and the insulating portion 20 c. The fifthmetal portion 15 is provided on the second insulating portion 22. Forexample, the fifth metal portion 15 is provided inside an insulatingportion 20 d. The conductive layer 52 b is provided between the fifthmetal portion 15 and the insulating portion 20 d.

The fourth metal portion 14 and the fifth metal portion 15 are coilsprovided in spiral configurations along the X-Y plane. The fourth metalportion 14 and the fifth metal portion 15 oppose each other in theZ-direction. In other words, the fifth metal portion 15 is provided tooverlap the fourth metal portion 14 in FIG. 22 when viewed from theZ-direction.

The sixth metal portion 16 surrounds the fourth metal portion 14 and thefifth metal portion 15 in the X-direction and the Y-direction. The sixthmetal portion 16 is connected to the reference potential. As illustratedin FIG. 24, the sixth metal portion 16 includes a fourth portion 16 d, afifth portion 16 e, and a sixth portion 16 f.

The fourth portion 16 d is provided around the fourth metal portion 14in the X-direction and the Y-direction. For example, the fourth portion16 d is provided inside the insulating portion 20 c. The conductivelayer 53 b is provided between the fourth portion 16 d and theinsulating portion 20 c.

The fifth portion 16 e is provided on a portion of the fourth portion 16d. The second insulating portion 22 is provided on another portion ofthe fourth portion 16 d. The conductive layer 54 b is provided betweenthe fifth portion 16 e and the fourth portion 16 d and between the fifthportion 16 e and the second insulating portion 22.

The sixth portion 16 f is provided around the fifth metal portion 15 inthe X-direction and the Y-direction. For example, the sixth portion 16 fis provided inside the insulating portion 20 d. The conductive layer 55b is provided between the sixth portion 16 f and the insulating portion20 d.

As illustrated in FIG. 24, the third layer 33 is provided around thebottom portion of the fifth portion 16 e. The third layer 33 contactsthe conductive layer 54 b and the other portion of the fourth portion 16d recited above. Therefore, the second insulating portion 22 does notcontact the fourth portion 16 d and is separated from the fourth portion16 d in the Z-direction.

The third insulating layer 43 is provided between the fourth metalportion 14 and the second insulating portion 22. The third insulatinglayer 43 may contact the fourth metal portion 14 or may be separatedfrom the fourth metal portion 14 in the Z-direction.

The fourth layer 34 is provided on the second insulating portion 22. Thefourth layer 34 is provided around the bottom portion of the sixthportion 16 f and around the bottom portion of the fifth metal portion 15and contacts the conductive layers 52 b and 55 b. The fourth insulatinglayer 44 is provided on the fourth layer 34 and contacts the conductivelayers 52 b and 55 b.

In the digital isolator 160, the third layer 33 is insulative. The thirdlayer 33 is provided also between the fourth metal portion 14 and thethird insulating layer 43 and contacts the fourth metal portion 14. Thethird insulating layer 43 is positioned between the third layer 33 andthe second insulating portion 22. The third insulating layer 43 isprovided also between the second insulating portion 22 and the otherportion of the fourth portion 16 d recited above and contacts theconductive layer 54 b.

One end of the first metal portion 11 is electrically connected to thefirst circuit 1 via wiring 60 a. The other end of the first metalportion 11 is electrically connected to the first circuit 1 by wiring 61a. An electrode pad 62 a is connected to one end of the second metalportion 12.

One end of the fourth metal portion 14 is electrically connected to thesecond circuit 2 via wiring 60 b. The other end of the fourth metalportion 14 is electrically connected to the second circuit 2 by wiring61 b. An electrode pad 62 b is connected to one end of the fifth metalportion 15.

The second metal portion 12 is electrically connected to the fifth metalportion 15. Specifically, the electrode pads 62 a and 62 b are connectedrespectively to the one end of the second metal portion 12 and the oneend of the fifth metal portion 15. The electrode pads 62 a and 62 b areelectrically connected by the bonding wire 63. Electrode pads 65 a and65 b are connected respectively to the other end of the second metalportion 12 and the other end of the fifth metal portion 15. Theelectrode pads 65 a and 65 b are electrically connected by a bondingwire 66.

Or, the electrode pad 62 a of the structure body 10-1 and the electrodepad 65 b of the structure body 10-2 may be connected by a bonding wire;and the electrode pad 65 b of the structure body 10-1 and the electrodepad 62 b of the structure body 10-2 may be connected by a bonding wire.In the digital isolator 160, the first circuit 1 is electricallyconnected to the first metal portion 11 of the structure body 10-1; andthe second circuit 2 is electrically connected to the fourth metalportion 14 of the structure body 10-2.

In the structure body 10-1, one end portion of the first metal portion11 may be electrically connected to the third metal portion 13. The oneend portion of the first metal portion 11 may be connected to thereference potential by wiring, etc., other than the third metal portion13. In the structure body 10-2, one end portion of the fourth metalportion 14 may be electrically connected to the sixth metal portion 16.The one end portion of the fourth metal portion 14 may be connected tothe reference potential by wiring, etc., other than the sixth metalportion 16.

The fourth metal portion 14, the fifth metal portion 15, and the sixthmetal portion 16 include metals. From the perspective of reducing theelectrical resistances, it is favorable for the fourth metal portion 14and the fifth metal portion 15 to include copper.

The second insulating portion 22 includes an insulating material such assilicon oxide, etc.

The conductive layers 51 b to 55 b include tantalum. The conductivelayers 51 b to 55 b may include a nitride of tantalum. The conductivelayers 51 b to 55 b may have a stacked structure of tantalum and anitride of tantalum.

The third layer 33 and the fourth layer 34 include carbon, silicon, andat least one selected from the group consisting of oxygen and nitrogen.For example, the third layer 33 and the fourth layer 34 include SiCO,SiCN, or SiCON. The material that is included in the fourth layer 34 maybe different from the material included in the third layer 33.

The third insulating layer 43 and the fourth insulating layer 44 includesilicon nitride.

The carbon concentration in the third layer 33 is higher than the carbonconcentration in the third insulating layer 43. The Young's modulus ofthe third layer 33 is lower than the Young's modulus of the thirdinsulating layer 43. Similarly, the carbon concentration in the fourthlayer 34 is higher than the carbon concentration in the fourthinsulating layer 44 and higher than the carbon concentration in thethird insulating layer 43. The Young's modulus of the fourth layer 34 islower than the Young's modulus of the fourth insulating layer 44 andlower than the Young's modulus of the third insulating layer 43. Thecarbon concentration in the third layer 33 may be the same as ordifferent from the carbon concentration in the fourth layer 34. On theother hand, to improve the insulative properties, it is favorable forthe third insulating layer 43 and the fourth insulating layer 44 to beformed without adding carbon.

For example, the carbon concentration in the third layer 33 and thecarbon concentration in the fourth layer 34 each are not less than 15atom % and not more than 25 atom % in atomic composition percent. Thecarbon concentration in the third insulating layer 43 and the carbonconcentration in the fourth insulating layer 44 each are not less than 0atom % and not more than 10 atom % in atomic composition percent.

By providing the third layer 33 and the fourth layer 34, the peeling ofthe third insulating layer 43 and the fourth insulating layer 44 can besuppressed; and the reliability of the digital isolator 170 can beincreased.

In FIG. 24, the case is described where the configuration of thestructure body 10-2 is similar to that of the digital isolator 100. Theconfiguration is not limited to the example; and the configuration ofthe structure body 10-2 may be similar to that of one of the digitalisolators 110 to 130. Or, the configuration of the structure body 10-1may be similar to that of the digital isolator 140; and the firstinsulating layer 41 and the second insulating layer 42 may not beprovided in the structure body 10-1.

The structure body 10-1 and the structure body 10-2 may be provided onthe same substrate or may be configured as one chip. The structure body10-1 and the structure body 10-2 may be provided on different substratesor may be configured as separate chips. In the case where the structurebody 10-1 and the structure body 10-2 are provided on the samesubstrate, one common layer may be provided as the first layer 31 andthe third layer 33. Similarly, one common layer may be provided as thesecond layer 32 and the fourth layer 34. One common insulating layer maybe provided as the first insulating layer 41 and the third insulatinglayer 43. One common insulating layer may be provided as the secondinsulating layer 42 and the fourth insulating layer 44. One commoninsulating portion may be provided as the first insulating portion 21and the second insulating portion 22.

The second circuit 2 transmits a signal (a current) to the first metalportion 11 of the structure body 10-2. When a current flows in the firstmetal portion 11 and a magnetic field is generated, a current flows inthe second metal portion 12 due to an induced electromotive force. Atthis time, a current flows also in the fifth metal portion 15 of thestructure body 10-1 which is electrically connected to the second metalportion 12. When the current flows in the fifth metal portion 15 and amagnetic field is generated, a current flows in the fourth metal portion14 due to an induced electromotive force. The first circuit 1 detectsthe current flowing in the fourth metal portion 14 and generates asignal corresponding to the detection result. Thereby, the signal istransmitted between the first circuit 1 and the second circuit 2 via thepair of structure bodies 10.

Seventh Modification

FIG. 25 is a cross-sectional view illustrating a portion of a digitalisolator according to a seventh modification of the embodiment.

In the digital isolator 170 according to the seventh modification asillustrated in FIG. 25, the first metal portion 11 and the second metalportion 12 have flat plate configurations instead of spiralconfigurations. For example, the first metal portion 11 and the secondmetal portion 12 are provided so that the upper surface of the firstmetal portion 11 and the lower surface of the second metal portion 12are parallel.

Instead of the change of a magnetic field, the digital isolator 170transmits a signal by utilizing the change of an electric field.Specifically, an electric field is generated between the first metalportion 11 and the second metal portion 12 when the second circuit 2applies a voltage to the second metal portion 12. A charge thatcorresponds to the electric field intensity is stored in the first metalportion 11. The first circuit 1 detects the flow of the charge at thistime and generates a signal based on the detection result. Thereby, thesignal is transmitted in a state in which the current is blocked betweenthe first metal portion 11 and the second metal portion 12.

Other than the structure relating to the first metal portion 11 and thesecond metal portion 12, the structure of the digital isolator 170 issimilar to that of the digital isolator 100. Accordingly, according tothe digital isolator 170, similarly to the digital isolator 100, thepeeling of the first insulating layer 41 and the second insulating layer42 due to the stress of the conductive layers 54 and 55 can besuppressed. Also, the electrical resistance between the first metalportion 11 and the second metal portion 12 can be increased; and theleakage current between these metal portions can be reduced.

The structures of the modifications described above can be performed incombination as appropriate. For example, the structures of the firstlayer 31 and the first insulating layer 41 of one of the digitalisolators 100 to 120 may be combined with the structures of the secondlayer 32 and the second insulating layer 42 of another one of thedigital isolators 100 to 120. The first metal portion 11 and the secondmetal portion 12 may have flat plate configurations in the digitalisolators 100, 110, 120, 130, 140, 151, or 152. The first metal portion11, the second metal portion 12, the fourth metal portion 14, and thefifth metal portion 15 may have flat plate configurations in the digitalisolator 160. The structures of the first layer 31, the second layer 32,the first insulating layer 41, and the second insulating layer 42 of thedigital isolator 110 or 120 are applicable to those of the digitalisolator 170. The first insulating layer 41 and the second insulatinglayer 42 may not be provided in the digital isolator 170. Or, the gapsG1 and G2 may be provided instead of the first layer 31 and the secondlayer 32 in the digital isolator 140.

The embodiment may include the following configurations.

(Configuration 1)

A digital isolator, comprising:

a first metal portion;

a first insulating portion provided on the first metal portion;

a second metal portion provided on the first insulating portion;

a third metal portion including

-   -   a first portion provided around the first metal portion in a        direction perpendicular to a first direction, the first        direction being from the first metal portion toward the second        metal portion,    -   a second portion provided on a portion of the first portion with        a first conductive layer interposed, the first conductive layer        including tantalum, and    -   a third portion provided on the second portion and provided        around the second metal portion in the perpendicular direction;        and

a first insulating layer contacting an other portion of the firstportion and being provided around a bottom portion of the secondportion, a gap being provided between the first conductive layer and thefirst insulating layer.

(Configuration 2)

The isolator according to configuration 1, wherein the first insulatinglayer is provided also between the first metal portion and the firstinsulating portion.

(Configuration 3)

The isolator according to configuration 1, further comprising a secondinsulating layer provided around a bottom portion of the third portion,

the third portion being provided on the second portion with a secondconductive layer interposed, the second conductive layer includingtantalum,

the second insulating layer and the second conductive layer having a gapprovided between the second insulating layer and the first conductivelayer. In the embodiments described above, for example, the elementsthat are included in each component and the concentrations of theelements can be measured by SIMS (secondary ion mass spectrometry),energy dispersive X-ray spectrometry (EDX), etc.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the invention. The above embodiments can be practiced incombination with each other.

1. A digital isolator, comprising: a first metal portion; a firstinsulating portion provided on the first metal portion; a second metalportion provided on the first insulating portion; a third metal portionincluding a first portion provided around the first metal portion in adirection perpendicular to a first direction, the first direction beingfrom the first metal portion toward the second metal portion; a secondportion provided on a portion of the first portion with a firstconductive layer interposed, the first conductive layer includingtantalum; a third portion provided on the second portion and providedaround the second metal portion in the perpendicular direction; and afirst layer contacting the first conductive layer and an other portionof the first portion and being provided around a bottom portion of thesecond portion, the first layer including titanium or including siliconand carbon.
 2. The isolator according to claim 1, further comprising afirst insulating layer provided between the first metal portion and thefirst insulating portion.
 3. The isolator according to claim 2, whereinthe first insulating layer contacts the first conductive layer and isprovided also between the first insulating portion and the other portionof the first portion, and at least a portion of the first insulatinglayer is positioned between the first layer and the first insulatingportion.
 4. The isolator according to claim 2, wherein the first layeris insulative, and the first layer is provided also between the firstmetal portion and the first insulating layer.
 5. The isolator accordingto claim 1, wherein the first layer includes carbon, silicon, and atleast one selected from the group consisting of oxygen and nitrogen, thefirst insulating layer includes nitrogen and silicon, and a carbonconcentration in the first layer is higher than a carbon concentrationin the first insulating layer.
 6. The isolator according to claim 2,wherein the first insulating layer is not provided between the firstlayer and the first insulating portion.
 7. The isolator according toclaim 1, wherein the first layer is not provided between the first metalportion and the first insulating portion.
 8. The isolator according toclaim 7, wherein the first layer is conductive or semiconductive.
 9. Theisolator according to claim 1, further comprising a second layerprovided around a bottom portion of the third portion, the third portionbeing provided on the second portion with a second conductive layerinterposed, the second conductive layer including tantalum, the secondlayer contacting the second conductive layer, the second layer includingtitanium or including silicon and carbon.
 10. The isolator according toclaim 1, further comprising: a second layer provided around a bottomportion of the third portion; and a second insulating layer provided onthe second layer, the third portion being provided on the second portionwith a second conductive layer interposed, the second conductive layerincluding tantalum, the second layer contacting the second conductivelayer, a Young's modulus of the second layer being lower than a Young'smodulus of the second insulating layer.
 11. The isolator according toclaim 1, wherein the first metal portion and the second metal portionare provided in spiral configurations along a plane perpendicular to thefirst direction.
 12. The isolator according to claim 11, wherein one endof the first metal portion is electrically connected to the firstportion, or one end of the second metal portion is electricallyconnected to the third portion.
 13. The isolator according to claim 1,wherein the first metal portion and the second metal portion areprovided in flat plate configurations along a plane perpendicular to thefirst direction.
 14. The isolator according to claim 1, furthercomprising: a first circuit electrically connected to the first metalportion; and a second circuit electrically connected to the second metalportion.
 15. A digital isolator, comprising: a first metal portion; afirst insulating portion provided on the first metal portion; a secondmetal portion provided on the first insulating portion; a third metalportion including a first portion provided around the first metalportion in a direction perpendicular to a first direction, the firstdirection being from the first metal portion toward the second metalportion, a second portion provided on a portion of the first portionwith a first conductive layer interposed, the first conductive layerincluding tantalum, and a third portion provided on the second portionand provided around the second metal portion in the perpendiculardirection; a first layer contacting the first conductive layer and another portion of the first portion and being provided around a bottomportion of the second portion; and a first insulating layer providedbetween the first metal portion and the first insulating portion, aYoung's modulus of the first layer being lower than a Young's modulus ofthe first insulating layer.
 16. The isolator according to claim 15,wherein the first layer includes titanium.
 17. The isolator according toclaim 15, wherein the first layer includes silicon and carbon. 18.(canceled)
 19. (canceled)
 20. (canceled)